1. Field of the Invention
The invention relates to a touch pen for a touch device, and more particularly to a light-emitting touch pen for an optical touch device.
2. Description of the Related Art
FIG. 1 illustrates a conventional touch pen, which serves as a pointing pen for an optical touch device (not shown). The conventional touch pen includes a pen barrel 11, a light-transmissive tip body 13 mounted to the pen barrel 11 and having an exposed portion 131 that extends outwardly of the pen barrel 11 in an axial direction of the pen barrel 11, and a light source 12 (such as an LED) mounted coaxially in the pen barrel 11 and disposed adjacent to the tip body 13 such that light emitted by the light source 12 radiates out through the exposed portion 131 of the tip body 13. When the tip body 13 touches a touch screen 100 of the optical touch device (see FIG. 2), the light radiated from the exposed portion 131 of the tip body 13 is sensed by an optical sensor module (not shown) of the optical touch device, such that a sensed position (P′) associated with a touch point of the tip body 13 on the touch screen 100 is determined by the optical touch device and is displayed on the touch screen 100.
It is noted that the exposed portion 131 of the tip body 13 has a length ranging from 5 mm to 6 mm. As a result, when the tip body 13 touches the touch screen 100, a position on the touch screen 100, which corresponds to a central point (C) of the exposed portion 131 of the tip body 13 (see FIG. 2), is determined by the optical touch device as the sensed position (P′).
In use, as shown in FIG. 2, when the conventional touch pen inclinedly touches the touch screen 100 with the tip body 13, there is a displacement (Δd) between a position (P) of a touch point of the tip body 13 on the touch screen 100 and the sensed position (P′) associated with the touch point of the tip body 13 and displayed on the touch screen 100. In this case, the optical touch device locates the touch point of the tip body 13 on the touch screen 100 with reduced accuracy. It should be noted that the longer the length of the exposed portion 131 of the tip body 13, the greater the displacement (Δd). Therefore, when such touch pen is used with the optical touch device, the optical touch device may not ensure accuracy in locating a touch point on the touch screen 100.